To picture, say, Earth's Trojan asteroid, imagine the sun and Earth as being two points in a triangle whose sides are equal in length. The other point of such a triangle is known as a Trojan point, or a Lagrangian point, named after the mathematician who discovered them. At such a point, the gravitational attraction of the sun and Earth essentially balances out, meaning they are relatively stable points for asteroids or other objects.

Technically, the Lagrangian points do not provide stable parking spots for objects, because the slightest movement away from them puts the object in a position where the net gravitational attraction is no longer zero. The spacecraft that are parked at Lagrangian points have to constantly apply small thrusts to move back into the zero-gravity spots.

R.R. thanks for posting this... wow what a strange object indeed, it has a really rapid rotation! Only a third the size of Earth. "THREE HAUMEAS COULD FIT SIDE BY SIDE IN EARTH."

"It takes 3.9 hours for Haumea to make a full rotation, which means it has by far the fastest spin, and thus shortest day, of any object in the solar system larger than 62 miles."

Haumea is a trans-Neptunian object; its orbit, in other words, is beyond that of the farthest ice giant in the solar system. Its discovery was reported to the International Astronomical Union in 2005, and its status as a dwarf planet—the fifth, after Ceres, Eris, Makemake, and Pluto—was made official three years later.

Technically, the Lagrangian points do not provide stable parking spots for objects, because the slightest movement away from them puts the object in a position where the net gravitational attraction is no longer zero. The spacecraft that are parked at Lagrangian points have to constantly apply small thrusts to move back into the zero-gravity spots.

Technically, the Lagrangian points do not provide stable parking spots for objects, because the slightest movement away from them puts the object in a position where the net gravitational attraction is no longer zero. The spacecraft that are parked at Lagrangian points have to constantly apply small thrusts to move back into the zero-gravity spots.

Thanks Jim, for that clarification.

Oops! Digging deeper, I discovered this:" The unstable Lagrange points - labeled L1, L2 and L3 - lie along the line connecting the two large masses. The stable Lagrange points - labeled L4 and L5 - form the apex of two equilateral triangles that have the large masses at their vertices. L4 leads the orbit of earth and L5 follows "